I've had to create multiple Excel or Word files when I'm evolving a document.
That's why I save the file under different version names, e.g. Financial
Spreadsheet 12-20-04 1030am.xls, Financial Spreadsheet 12-21-04.xls, etc...

How do effectively create versions of the data to avoid creating multiple
files?
Now that I have multiple files, how do I perform a "diff" to compare them to
ensure I haven't lost any important data from an earlier version that I may
want to retain?

Thank you.